The invention relates to hybrid vehicles having a drive unit in addition to a conventional internal combustion engine and a control method for the energy demand required by drive train of such a vehicle.
Future generations of vehicles will be increasingly equipped with hybrid drives. Hybrid drives have an additional drive unit alongside the conventional internal combustion engine. This additional drive unit is frequently an electric motor which is supplied with energy via a re-chargeable energy accumulator, for example a battery. In comparison to conventional drives, hybrid drives have a multiplicity of additional operating states of the drive train. In addition to a purely internal combustion engine mode, a purely electromotive mode, and a combined mode are also possible. Furthermore, a distinction can be made between operating states with charging of the battery and operating states without charging of the battery.
Energy may be stored in a hybrid vehicle in the fluid fuel, and/or in the energy accumulator. In order to use that energy as efficiently as possible, and thus avoid overdimensioning of individual components of the drive train, stringent requirements are placed on the control of the drive train. Depending on the operating state of the drive train, different quantities of energy are extracted from the fuel and the energy accumulator, or different quantities of energy are fed into the energy accumulator. In the control, consideration is to be given in particular to the fact that the characteristics of the route which is to be traveled will have an influence on the required quantity of energy, or the quantity of energy which is to be recovered.
Future generations of vehicles will frequently be equipped with a navigation system or similar components which permit the characteristics of the route which is to be traveled to be predicted, thus permitting the expected energy demand to be estimated.
DE 198 31 487 C1 discloses a method for operating a hybrid drive of a vehicle which has a battery, and in which information relating to a route to be traveled is sensed. Expected power requirements of the hybrid drive over the course of the route are calculated taking this information into account, and a timetable, which controls the control of the individual drive components or modes of operation, is determined as a function of the calculated power requirements, taking into account the levels of efficiency of the drive components or modes of operation.
The object of the present invention is to provide an optimum control for the drive train of a hybrid vehicle in terms of the energy demand, which takes into account driving situations and routes to be traveled. According to the invention, data which characterizes at least a portion of the route to be traveled is requested. Based on this data, an operating strategy is defined for the individual components of the drive train. The expected energy demand is calculated as a function of the operating strategy and of the route data. Subsequently a time period for which the calculated energy can be made available is calculated. If the calculated time period is detected as being sufficient, the individual components of the drive train are controlled in accordance with the operating strategy. If the calculated time period is, on the other hand, detected as not being sufficient, an alternative operating strategy is defined and the resulting time period is checked again.